Malfunction determination apparatus for cooling apparatus and malfunction determination method for cooling apparatus

Abstract

In a malfunction determination apparatus and a malfunction determination method for a cooling apparatus that cools an internal combustion engine by circulating a cooling medium that flows in a first passage that extends through an inside of the engine, using an electric pump, a first temperature of the cooling medium is detected at an inlet of the first passage, through which the cooling medium flows into the inside of the engine; a second temperature of the cooling medium is detected at an outlet of the first passage, through which the cooling medium flows out from the inside of the engine; and it is determined that the switching valve is able to normally select the second passage, if both of the first temperature and the second temperature reach a first threshold value when a temperature of the cooling medium increases due to start of the engine.

What is claimed is: 
     
       1. A malfunction determination apparatus for a cooling apparatus that cools an internal combustion engine by circulating a cooling medium that flows in a first passage that extends through an inside of the internal combustion engine, using an electric pump, wherein the cooling apparatus includes a radiator, a second passage for circulating the cooling medium to the first passage so that the cooling medium bypasses the radiator, a third passage for circulating the cooling medium to the first passage via the radiator, and a switching valve that switches a flow passage for the cooling medium from a flow passage including the second passage to a flow passage including the third passage, in response to an increase in a temperature of the cooling medium after the internal combustion engine is started, the malfunction determination apparatus comprising:
 an inlet temperature detection portion that detects a first temperature of the cooling medium at an inlet of the first passage, through which the cooling medium flows into the inside of the internal combustion engine; 
 an outlet temperature detection portion that detects a second temperature of the cooling medium at an outlet of the first passage, through which the cooling medium flows out from the inside of the internal combustion engine; and 
 a normal function determination portion that determines that the switching valve is able to normally select the second passage, if both of the first temperature and the second temperature reach a first threshold value when the temperature of the cooling medium increases due to start of the internal combustion engine. 
 
     
     
       2. The malfunction determination apparatus according to  claim 1 , wherein the inlet temperature detection portion that detects the first temperature of the cooling medium at the inlet of the first passage, through which the cooling medium flows into the inside of the internal combustion engine, is positioned between the switching valve and the internal combustion engine. 
     
     
       3. The malfunction determination apparatus according to  claim 1 , further comprising:
 a control portion that stops the electric pump if the second temperature is lower than a second threshold value, and operates the electric pump if the second temperature is equal to or higher than the second threshold value. 
 
     
     
       4. The malfunction determination apparatus according to  claim 3 , further comprising:
 an estimation portion that estimates the temperature of the cooling medium based on a state of the internal combustion engine after an operation of the internal combustion engine is started; and 
 a malfunction determination portion that determines that the switching valve is malfunctioning, if the second temperature falls below a third threshold value that is equal to or lower than the first threshold value due to an operation of the electric pump, after the temperature estimated by the estimation portion reaches the first threshold value. 
 
     
     
       5. The malfunction determination apparatus according to  claim 4 , wherein
 the control portion operates the electric pump, independently of the operation of the internal combustion engine. 
 
     
     
       6. A malfunction determination method for a cooling apparatus that cools an internal combustion engine by circulating a cooling medium that flows in a first passage that extends through an inside of the internal combustion engine, using an electric pump, wherein the cooling apparatus includes a radiator, a second passage for circulating the cooling medium to the first passage so that the cooling medium bypasses the radiator, a third passage for circulating the cooling medium to the first passage via the radiator, and a switching valve that switches a flow passage for the cooling medium from a flow passage including the second passage to a flow passage including the third passage, in response to an increase in a temperature of the cooling medium after the internal combustion engine is started, the malfunction determination method comprising:
 detecting a first temperature of the cooling medium at an inlet of the first passage, through which the cooling medium flows into the inside of the internal combustion engine; 
 detecting a second temperature of the cooling medium at an outlet of the first passage, through which the cooling medium flows out from the inside of the internal combustion engine; and 
 determining that the switching valve is able to normally select the second passage, if both of the first temperature and the second temperature reach a threshold value when the temperature of the cooling medium increases due to start of the internal combustion engine. 
 
     
     
       7. The malfunction determination method according to  claim 6 , wherein the first temperature of the cooling medium at the inlet of the first passage, through which the cooling medium flows into the inside of the internal combustion engine, is detected between the switching valve and the internal combustion engine. 
     
     
       8. A malfunction determination apparatus for a cooling apparatus that cools an internal combustion engine by circulating a cooling medium that flows in a first passage that extends through an inside of the internal combustion engine, using an electric pump, wherein the cooling apparatus includes a radiator, a second passage for circulating the cooling medium to the first passage so that the cooling medium bypasses the radiator, a third passage for circulating the cooling medium to the first passage via the radiator, and a switching valve that switches a flow passage for the cooling medium from a flow passage including the second passage to a flow passage including the third passage, in response to an increase in a temperature of the cooling medium after the internal combustion engine is started, the malfunction determination apparatus comprising:
 an inlet temperature detection portion that detects a first temperature of the cooling medium at an inlet of the first passage, through which the cooling medium flows into the inside of the internal combustion engine; 
 an outlet temperature detection portion that detects a second temperature of the cooling medium at an outlet of the first passage, through which the cooling medium flows out from the inside of the internal combustion engine; and 
 a normal function determination portion that determines that the switching valve is able to normally select the second passage, if the first temperature reaches a first threshold value and the second temperature reach a fourth threshold value when the temperature of the cooling medium increases due to start of the internal combustion engine. 
 
     
     
       9. The malfunction determination apparatus according to  claim 8 , wherein the inlet temperature detection portion that detects the first temperature of the cooling medium at the inlet of the first passage, through which the cooling medium flows into the inside of the internal combustion engine, is positioned between the switching valve and the internal combustion engine. 
     
     
       10. The malfunction determination apparatus according to  claim 8 , further comprising:
 a control portion that stops the electric pump if the second temperature is lower than a second threshold value, and operates the electric pump if the second temperature is equal to or higher than the second threshold value. 
 
     
     
       11. The malfunction determination apparatus according to  claim 10 , further comprising:
 an estimation portion that estimates the temperature of the cooling medium based on a state of the internal combustion engine after an operation of the internal combustion engine is started; and 
 a malfunction determination portion that determines that the switching valve is malfunctioning, if the second temperature falls below a third threshold value that is equal to or lower than the first threshold value due to an operation of the electric pump, after the temperature estimated by the estimation portion reaches the first threshold value. 
 
     
     
       12. The malfunction determination apparatus according to  claim 11 , wherein
 the control portion operates the electric pump, independently of the operation of the internal combustion engine. 
 
     
     
       13. A malfunction determination method for a cooling apparatus that cools an internal combustion engine by circulating a cooling medium that flows in a first passage that extends through an inside of the internal combustion engine, using an electric pump, wherein the cooling apparatus includes a radiator, a second passage for circulating the cooling medium to the first passage so that the cooling medium bypasses the radiator, a third passage for circulating the cooling medium to the first passage via the radiator, and a switching valve that switches a flow passage for the cooling medium from a flow passage including the second passage to a flow passage including the third passage, in response to an increase in a temperature of the cooling medium after the internal combustion engine is started, the malfunction determination method comprising:
 detecting a first temperature of the cooling medium at an inlet of the first passage, through which the cooling medium flows into the inside of the internal combustion engine; 
 detecting a second temperature of the cooling medium at an outlet of the first passage, through which the cooling medium flows out from the inside of the internal combustion engine; and 
 determining that the switching valve is able to normally select the second passage, if the first temperature reaches a first threshold value and the second temperature reach a fourth threshold value when the temperature of the cooling medium increases due to start of the internal combustion engine. 
 
     
     
       14. The malfunction determination method according to  claim 13 , wherein the first temperature of the cooling medium at the inlet of the first passage, through which the cooling medium flows into the inside of the internal combustion engine, is detected between the switching valve and the internal combustion engine.